Class 10 Science Chapter 13 Case Based Questions - Our Environment

Case Study - 1

All organisms such as plants, animals, microorganisms and human beings as well as the physical surroundings interact with each other and maintain a balance in nature. All the interacting organisms in an area together with the non-living constituents of the environment form an ecosystem. Thus, an ecosystem consists of biotic components comprising living organisms and abiotic components comprising physical factors like temperature, rainfall, wind, soil and minerals.

Q1: What is natural ecosystem?
Ans: An environment where living organism and non- living interact with each other freely in nature is called as natural ecosystem.

Q2: what are the examples of artificial ecosystem?
Ans: Gardens, crop- fields

Q3: What are consumers?
Ans: Organism which consume food either directly or indirectly by feeding on one another animals are called as consumers.

Q4: What are the type of consumers?
Ans: They are herbivores, carnivores, omnivores and parasites.

Q5: What are producers?
Ans: The green plants and some bacteria which make their food by using sunlight i.e photosynthesis are called as producers.

Case Study - 2

The food we eat acts as a fuel to provide us energy to do work. Thus the interactions among various components of the environment involves flow of energy from one component of the system to another. As we have studied, the autotrophs capture the energy present in sunlight and convert it into chemical energy. This energy supports all the activities of the living world. From autotrophs, the energy goes to the heterotrophs and decomposers.

Q1: What is food chain?
Ans: A series of organism feeding on one another and taking part in various biotic levels is called food chain.

Q2: Give a example of one terrestrial food chain.
Ans: Sunlight ⇒ plants (producers) ⇒ Goat/ Deer (herbivores) ⇒ Tiger (carnivores)

Q3: What are the feature of food chain?
Ans: It is unidirectional
The energy available at each level gets diminished due to loss at each level.

Q4: What do you meant by biological magnification?
Ans: The gradual increase in the concentration of any substance ( generally toxic) in trophic levels is called as biological magnification.

Q5: What is the average value for the amount of organic matter that is present at each step and reaching the next level of consumers?
Ans: 10%

Case Study - 3

In our daily activities, we generate a lot of material that are thrown away. What are some of these waste materials? What happens after we throw them away? Let us perform an activity to find answers to these questions.

• Collect waste material from your homes. This could include all the waste generated during a day, like kitchen waste (spoilt food, vegetable peels, used tea leaves, milk packets and empty cartons), waste paper, empty medicine bottles/strips/bubble packs, old and torn clothes and broken footwear.
• Bury this material in a pit in the school garden or if there is no space available, you can collect the material in an old bucket/ flower pot and cover with at least 15 cm of soil.
• Keep this material moist and observe at 15-day intervals.
• What are the materials that remain unchanged over long periods of time?
• What are the materials which change their form and structure over time?
• Of these materials that are changed, which ones change the fastest?

We have seen in the chapter on ‘Life Processes’ that the food we eat is digested by various enzymes in our body. Have you ever wondered why the same enzyme does not break-down everything we eat? Enzymes are specific in their action, specific enzymes are needed for the break-down of a particular substance. That is why we will not get any energy if we try to eat coal! Because of this, many human-made materials like plastics will not be broken down by the action of bacteria or other saprophytes. These materials will be acted upon by physical processes like heat and pressure, but under the ambient conditions found in our environment, these persist for a long time.

Q1: What is biodegradable substances?
Ans: The substances that are broken down by biological process are called as biodegradable substances.
Example: Vegetables waste materials.

Q2: What are the examples of non- biodegradable substances?
Ans: Plastic, rubber, foam, batteries etc.

Q3: What are the ways through which we can reduce pollution especially the non- biodegradable waste?
Ans: 

• We can use RRR methods i.e reduce, reuse and recycle. 
• Reduce the use of plastic.

Q4: What are the effects of biodegradable substances on our environment?
Ans:

• Release green house gases.
• They are breeding ground for mosquitoes and houseflies causing various disease.

Q5: What are the non- biodegradable on environment?
Ans: 

• causes soil pollution and sometimes air pollution when burnt in air.
• death of cattles due to ingestion of these waste.
• choking of drainage system.

Case Study - 4

We are an integral part of the environment. Changes in the environment affect us and our activities change the environment around us
Ozone (O3 ) is a molecule formed by three atoms of oxygen. While O2 , which we normally refer to as oxygen, is essential for all aerobic forms of life. Ozone, is a deadly poison. However, at the higher levels of the atmosphere, ozone performs an essential function. It shields the surface of the earth from ultraviolet (UV) radiation from the Sun.

Q1: How does ozone is formed?
Ans: The UV radiations coming from the sun split the molecular oxygen into nascent oxygen. When these nascent oxygen combined to molecular oxygen, it forms ozone(O3).

Q2: In which layer of atmosphere does ozone is present?
Ans: The ozone is present in the stratosphere layer of atmosphere just above troposphere.

Q3: What are the causes for ozone depletion?
Ans: The synthetic chemicals like CFCs (chlorofluorocarbons) which used as refrigerants amd in the fire extinguisher.

Q4: Write the chemical reaction for the formation of ozone?
Ans:  O2  ⇒  [O] + [O]
[O]  + O2 ⇒ O3 (ozone)

Q5: What are the effects of UV radiations?
Ans: It causes different types of cancer in human beings.

Case study – 5

In Kunjpura village, located in Karnal district, Haryana, Aditya Aggarwal and his older brother Amit Aggarwal run Tee Cee Industries, a steel plant set up by their ancestors in 1984. Along with this, they also run a gaushala that houses 1,200 cows that can no longer produce milk. The cow shelter was manageable but running the steel plant was turning out to be expensive because they spent a whopping Rs 5 lakh every month on electricity. The brothers struck upon an idea. Why not run the factory with the biogas produced from cow dung from the shelter and other gaushalas, along with bio and agri led Aditya and Amit to start Amrit Fertilizers, a biogas project, in 2014, without any government support.

Q1: Raw material used in bio gas plant is
(a) Animal dung
(b) Crop residue
(c) Food waste
(d) All of the above
Ans: (d)
Explanation: Biogas is produced through a process called anaerobic digestion, in which organic materials are broken down by microorganisms in the absence of oxygen. Various organic materials can be used as raw materials in a biogas plant, including animal dung, crop residues, and food waste. All of these materials are rich in organic matter, which serves as a source of energy for the microorganisms to produce biogas. Therefore, the correct answer is (d) All of the above.

Q2: Biogas is a better fuel than animal dung cake because
(i) Biogas has lower calorific value.
(ii) Animal dung cake has higher calorific value.
(iii) Biogas has high heating capacity.
(iv) Biogas burns without smoke.
(a) (i) only
(b) (ii) only
(c) (iii) and (iv)
(d) (i) and (ii)
Ans: (c)
Explanation: Biogas is a better fuel than animal dung cake for several reasons. Biogas has a higher calorific value compared to animal dung cake, meaning it releases more energy when burned. Additionally, biogas burns without producing smoke, making it a cleaner fuel option. The statements (iii) and (iv) are correct, as biogas indeed has a high heating capacity and burns without smoke. Therefore, the correct answer is (c) (iii) and (iv).

Q3: Biogas is formed in the
(a) presence of air only.
(b) presence of water only.
(c) absence of air only.
(d) presence of water and absence of air.
Ans: (d)
Explanation: Biogas is formed through the process of anaerobic digestion, which occurs in the absence of air (oxygen). The microorganisms that produce biogas thrive in an oxygen-free environment. However, the presence of water is also important for the process to take place. Water helps maintain the right conditions for the microorganisms to break down organic materials and produce biogas. Therefore, the correct answer is (d) presence of water and absence of air.

Q4: Biogas is a mixture of the following gases.
(a) Ethane, Carbon monoxide, Nitrogen and Butane
(b) Methane, Hydrogen, Carbon dioxide and Nitrogen
(c) Butane, Carbon monoxide, Propane and Hydrogen
(d) Carbon monoxide, Sulphur dioxide and Hydrogen
Ans: (b)
Explanation: Biogas is primarily composed of methane (CH4), which is the main combustible component and provides the energy content. It also contains smaller amounts of carbon dioxide (CO2), some traces of hydrogen (H2), and in some cases, small quantities of nitrogen (N2) and other gases. The option (b) correctly lists the main components of biogas, which are methane, hydrogen, carbon dioxide, and nitrogen. Therefore, the correct answer is (b) Methane, Hydrogen, Carbon dioxide and Nitrogen.

Case Study – 6

Food chains are very important for the survival of most species. When only one element is removed from the food chain it can result in extinction of a species in some cases. The foundation of the food chain consists of primary producers. Primary producers, or autotrophs, can use either solar energy or chemical energy to create complex organic compounds, whereas species at higher trophic levels cannot and so must consume producers or other life that itself consumes producers. Because the sun’s light is necessary for photosynthesis, most life could not exist if the sun disappeared. Even so, it has recently been discovered that there are some forms of life, chemotrophs, that appear to gain all their metabolic energy from chemosynthesis driven by hydrothermal vents, thus showing that some life may not require solar energy to thrive.

Q1: If 10,000 J solar energy falls on green plants in a terrestrial ecosystem, what percentage of solar energy will be converted into food energy?
(a) 10,000 J
(b) 100 J
(c) 1000 J
(d) It will depend on the type of the terrestrial plant
Ans: (b)
Explanation: The efficiency of energy conversion from solar energy to food energy in plants is generally low. Only a small fraction of the solar energy is converted through photosynthesis into food energy (organic matter). It's estimated that, on average, about 1% to 3% of the solar energy is converted into chemical energy in plants. Therefore, in this case, if 10,000 J of solar energy falls on green plants, approximately 100 J (1% of 10,000 J) would be converted into food energy. The correct answer is (b) 100 J.

Q2: Matter and energy are two fundamental inputs of an ecosystem. Movement of
(a) Energy is bidirectional and matter is repeatedly circulating.
(b) Energy is repeatedly circulation and matter is unidirectional.
(c) Energy is unidirectional and matter is repeatedly circulating.
(d) Energy is multidirectional and matter is bidirectional.
Ans: (c)
Explanation: In an ecosystem, energy flows in a unidirectional manner, usually from the Sun through producers (plants), consumers, and ultimately decomposers. Matter, on the other hand, circulates within the ecosystem through various biogeochemical cycles (such as the carbon cycle, nitrogen cycle, etc.), which involve the uptake, use, and recycling of elements like carbon, nitrogen, and other nutrients. Therefore, the correct answer is (c) Energy is unidirectional and matter is repeatedly circulating.

Q3: Mr. X is eating curd/yogurt. For this food intake in a food chain he should be considered as occupying
(a) First trophic level
(b) Second trophic level
(c) Third trophic level
(d) Fourth trophic level
Ans: (c)
Explanation: When Mr. X eats curd/yogurt, he is consuming a product derived from milk, which is obtained from animals such as cows. Since he is consuming a product derived from primary consumers (herbivores), he should be considered as occupying the third trophic level in the food chain. The primary producers (plants) form the first trophic level, the herbivores (consumers that eat plants) form the second trophic level, and the carnivores or omnivores that eat herbivores occupy higher trophic levels. Therefore, the correct answer is (c) Third trophic level.

Q4: Which of the following limits the number of trophic levels in a food chain?
(a) Decrease in energy at higher trophic levels
(b) Less availability of food
(c) Polluted air
(d) Water
Ans: (a)
Explanation: The decrease in energy at higher trophic levels is a key factor that limits the number of trophic levels in a food chain. As energy is transferred from one trophic level to the next, there is a significant loss of energy, usually in the form of heat, due to metabolic processes and inefficiencies in energy conversion. This decrease in available energy limits the amount of energy that can sustain organisms at higher trophic levels. As a result, there is typically a decrease in the number of trophic levels in a food chain, with fewer organisms occupying higher trophic levels. Therefore, the correct answer is (a) Decrease in energy at higher trophic levels.

Q5: The decomposers are not included in the food chain. The correct reason for the same is because decomposers:
(a) Act at every trophic level of the food chain
(b) Do not breakdown organic compounds
(c) Convert organic material to inorganic forms
(d) Release enzymes outside their body to convert organic material to inorganic forms
Ans: (a)
Explanation: The decomposers, such as bacteria and fungi, play a crucial role in breaking down organic matter and recycling nutrients in ecosystems. However, they do not occupy specific trophic levels in a linear food chain like producers and consumers do. Instead, decomposers act at every trophic level of the food chain and ecosystem by breaking down dead organic matter and returning nutrients to the soil, which are then taken up by plants. This cycling of nutrients is essential for the functioning of ecosystems but does not fit into the traditional linear structure of a food chain. Therefore, the correct reason is (a) Decomposers act at every trophic level of the food chain.